One handy use for Solaris Zones that I have come across recently, is a very quick and easy way to build packages. Rather than "polluting" the main filesystem tree with the software to be packaged, simply create a zone, install the software there, and as a final act, you can even prune unwanted parts of the tree before packaging it up and disposing of the zone.

I had some software to install into /usr/local; the existing tree includes some (non-essential) software already in /usr/local, so I created a full-root zone, cleaned /usr/local within the zone, built the software (configure && make && make install), which was actually Perl, some third-party libraries, and 30 or so modules, and tested it in the zone.